Convertible trailer

ABSTRACT

Trailers are described that include a chassis, a set of wheels for rollably supporting the chassis on the ground, and a rigid container carried by the chassis. The rigid container comprises a floor, a sidewall, an access door for loading/unloading materials into the container, and a convertible rigid roof. The convertible roof is movable between a closed position which permits waste or other materials to be compressed into the trailer, and an open position which permits the trailer to be loaded with bulk goods from the top. The convertible roof includes movable rigid panels, and a locking bar for holding the panels closed and connecting the opposite sidewalls of the trailer to each other against the expansion pressure exerted by loosely compressed materials transported in the trailer. The panels may be rotating panels hinged to a wall, or may be provided as sliding panels running in tracks.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.13/169,285, filed Sep. 7, 2011, which is a Continuation-in-Part of U.S.application Ser. No. 12/345,718, filed Dec. 30, 2008 (now U.S. Pat. No.7,967,357, issued Jun. 28, 2011) and entitled Convertible Trailer; theentire content of both applications is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to the field of transportation.More particularly, the present invention relates to a trailer for thetransportation of compacted garbage and/or bulk material.

BACKGROUND OF THE INVENTION

Garbage, waste, or any other materials, which are compacted fortransportation, require the use of fixed walled containers or trailers,which allow the transportation of materials in compacted form or thecompacting of the material in the container or trailer itself. Thesetypes of trailers cannot backhaul any bulk goods on the way back fromthe unloading site, as their fixed and closed top does not allow loadingfrom the top using a conventional loader, similar to an open-toptrailer.

With the rising cost of fuel, the disposal of garbage becomesincreasingly expensive, especially when the trailer cannot backhaul anygoods to reduce the cost of waste disposal, and thus, returns empty fromthe unloading site.

On the other hand, open top trailers, even those which include a cover,cannot be used for compacting or for the transport of loosely compactedmaterial.

United States Patent Application Publication No. 2007/0126209 (Wolfe)describes a trailer that converts into a shed. The trailer of Wolfeincludes a convertible roof comprising two panels. However, the panelscannot be locked, and the walls are not rigid enough to withstandcompressed materials.

European Patent Application No. 1,120,363 and United Kingdom PatentApplication No. 2,429,006 (Sumpter) describe a trailer for thecollection of waste comprising a chassis and a container. The containercomprises a roof including an aperture closeable by a cover that slidesover the aperture by means of a channel assembly. The cover may be apartly or fully retractable flexible sheet.

The structure of Sumpter does not allow the trailer to be used fortransporting loosely compressed materials because the materials aredistributed in the container using reciprocating slats, not a compactor.Furthermore, the cover disclosed in Sumpter is flexible and would thusnot be able to withstand any pressure from within the container. Sumpterclearly does neither teach nor suggest using the container disclosed fortransport of loosely compacted materials.

Neither Wolfe nor Sumpter deal with loosely compacted materials, andthus, fail to recognize the structural challenge created by internalpressures in a trailer upon compression of loose materials therein.

It is, therefore, desirable to provide a trailer that can accept andcontain loosely compacted material, and which can also backhaul bulkgoods on the way back from the unloading site in order to reduce thecost of transportation, which bulk goods are loaded from the top.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a trailer which canhold loosely compacted material or allows material to be compressedinside the trailer, but can also be loaded from the top to backhaul bulkgoods on the way back from an unloading site.

This specification refers to loosely compacted materials which arecompacted and maintained in the compacted condition solely by thetrailer without any secondary containment or bundling structures. Thus,loosely compacted materials continuously exert an expansion force on thecontainment structure in which they are held.

In an aspect, the invention provides a container for a convertibletrailer comprising a chassis for carrying the container and a set ofwheels for rollably supporting the chassis on the ground, the containercomprising a floor, a wall, and a roof, and an access door for loadingloosely compressed materials into the container. The roof includes apair of opposite rigid panels, respectively pivotally connected toopposite side walls of the container by multiple hinges for movementbetween a closed position wherein each panel forms part of a solid rooffor loading of the container with loosely compressed materials from theaccess door, and an open position wherein the container can be loadedfrom the top with bulk material. The container includes a plurality ofspaced apart locking bars distributed in longitudinal direction of theroof, for securing the panels in the closed position and forstrengthening the wall against outward pressure exerted by the looselycompressed materials when loaded in the container. Due to the unevenoutward pressure distribution along the length of the trailer whencompacting pressure is applied from the access opening, it is importantthat a spacing of the locking bars is smaller proximal to than distalfrom the access door.

The container is preferably rectangular including a rear wall, a frontwall and opposite sidewalls. In an embodiment, each locking bar ispreferably secured to one of the panels at one end and includes astructure for releasably fastening an opposite end to the other panelwhen the panels are in the closed position, for releasably locking thepanels in the closed position. In another embodiment, each locking baris preferably provided adjacent and substantially aligned with a pair ofhinges respectively connecting one of the panels to the associatedsidewall, for connecting the opposite sidewalls to each other by way ofthe locking bars and against the outward pressure exerted by the looselycompressed materials compacted in the trailer. Preferably, the lockingbars are positioned on the roof panels to be in symmetrical contact withthe roof panel on each side. The locking bars may be releasably fastenedat each end in order to allow for the complete removal of the lockingbars for opening of the roof panels in restricted space situations, orto allow the roof panels to be opened with the locking bars attached toone or the other of the roof panels.

In another aspect, the container includes a mid span tie bar connectinga top edge of the sidewalls mid span of the trailer for added structuralstrength of the basic trailer structure, and a locking bar locateddirectly above the tie bar. In another aspect, the number of lockingbars between the tie bar and an access door end of the container, theaccess door half of the roof, is higher than the number of locking barsbetween the tie bar and the other end on the trailer. The number oflocking bars on the access door half is preferably at least double thenumber on the other half. Most preferably, there are at least 6 lockingbars on the access door half of the roof for added stability, resistanceto movement and twisting and for resistance to compacting pressureexerted from the access opening.

In a further aspect of the invention, a rubber seal is provided betweeneach roof panel and edges of the container walls adjacent the panel inits closed position to minimize spillage of materials carried in thetrailer and intrusion of moisture and dirt into the container when theroof is closed. A rubber seal is preferably also provided between thepanels at their meeting edges. Finally, a seal is preferably provided atthe tie down bolt locations in order to minimize ingress ofcontamination into the container, especially during inclement weatherconditions.

In another aspect of the invention, the roof panels are extruded panelsand include edge extrusions for overlapping and interlocking engagementof the roof panels at their meeting edges when in the closed position.The edge extrusions are preferably constructed as a bottom overlapextrusion extending along the meeting edge of one panel and a topoverlap extrusion extending along the meeting edge of the other paneland complementary to the bottom overlap extrusion. Most preferably, theroof panels are extruded aluminum panels.

In a further aspect of the invention, each locking arm has an attachedhalf, which is rigidly welded to a first of the pair of roof panels anda free half for resting against and releasable attachment to the secondof the pair of roof panels, when the roof panels are in the closedposition. A rubber seal is preferably provided on the free end forcushioning between the free half and the second panel to preventgrinding of the locking bar against the second panel. A further rubberseal profile is preferably provided between the extruded aluminum roofpanel and the mid top tie bar for cushioning.

In still another aspect of the invention, the free end of the lockingbar is respectively releasably fastened to the second roof panel by atie down assembly. The assembly preferably includes a nut and boltconnection, with the nut welded to one of the roof panel and the lockingbar and the bolt extending through the other of the roof panel and thelocking bar for engaging the nut and fasten the locking bar to the roofpanel when the bolt is tightened in the nut.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings disclose illustrative embodiments. They do not set forthall embodiments. Other embodiments may be used in addition or instead.Details that may be apparent or unnecessary may be omitted to save spaceor for more effective illustration. Conversely, some embodiments may bepracticed without all of the details that are disclosed. When the samenumeral appears in different drawings, it refers to the same or likecomponents or steps.

Aspects of the disclosure may be more fully understood from thefollowing description when read together with the accompanying drawings,which are to be regarded as illustrative in nature, and not as limiting.The drawings are not necessarily to scale, emphasis instead being placedon the principles of the disclosure. In the drawings:

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 is a top view of a convertible trailer in accordance with anembodiment of the invention;

FIG. 2 is a rear view of the container of the trailer when the panelsare 90 degrees open;

FIG. 3 is a rear view of the container of the trailer when the panelsare fully open and the trailer is being loaded from the top;

FIG. 4 is an exploded view illustrating an embodiment of the invention,in which, the locking bar is provided at both panels;

FIG. 5 illustrates the rotation mechanism of the panels;

FIG. 6 illustrates a top plan view of a preferred container roofconstruction;

FIG. 7 illustrates a perspective top view of an end of the roofconstruction shown in FIG. 6;

FIG. 8 illustrates an enlarged view of one of the locking bars shown inFIG. 7;

FIG. 9 illustrates a cross-sectional view of the roof structure shown inFIG. 6, at the location of one of the locking bars;

FIG. 10 is a bottom perspective view of the mid portion of the roofconstruction shown in FIG. 6 and illustrating the mid span tie bar;

FIG. 11 illustrates a corner detail of the cross-sectional view of FIG.9;

FIG. 12 illustrates a center detail of the cross-sectional view of FIG.9;

FIG. 13 illustrates a hinge detail of the perspective view of FIG. 7;

FIG. 14 is a cross-sectional view of an end of the roof construction ofFIG. 7;

FIG. 15 is a cross-sectional view of a reverse tie down boltconstruction in the roof construction illustrated in FIG. 7;

FIG. 16 is a cross-sectional view of a variant of the tie down boltconstruction of FIG. 15; and

FIG. 17 is a cross-sectional view of the tie down bolt construction usedto engage the mid span tie bar.

While certain embodiments are depicted in the drawings, one skilled inthe art will appreciate that the embodiments depicted are illustrativeand that variations of those shown, as well as other embodimentsdescribed herein, may be envisioned and practiced within the scope ofthe present disclosure.

DETAILED DESCRIPTION

Generally, the present invention provides a container for looselycompacted materials which is convertible to a top loading bulk goodcontainer. In a preferred embodiment the invention provides a trailercomprising a chassis, a set of wheels for rollably supporting thechassis on the ground, and a rigid container carried by the chassis. Therigid container comprises a floor, a sidewall, an access door forloading/unloading materials into the container, and a convertible rigidroof. The convertible roof is movable between a closed position whichpermits waste or other materials to be compressed into the trailer, andan open position which permits the trailer to be loaded with bulk goodsfrom the top. The convertible roof includes movable rigid panels, and alocking bar for holding the panels closed and connecting the oppositesidewalls of the trailer to each other against the expansion pressureexerted by loosely compressed materials transported in the trailer. Thepanels may be rotating panels hinged to a wall, or may be provided assliding panels running in tracks.

FIG. 1 illustrates by way of example, a top view of a convertibletrailer 100 in accordance with an embodiment of the invention. In theembodiment shown in FIG. 1, the roof of the trailer is made of twomovable panels 102 and 104. When the panels 102 and 104 are in a closedposition, as illustrated in FIG. 1, the convertible trailer 100 may beloaded with loosely compressed materials, such as garbage, from theaccess door using a compactor (not shown). The compactor appliespressure on the materials loaded in order to remove gaps for the mostefficient use of the space inside the trailer. When the compactor isoperated, the roof must be closed and rigid in order to withstand theoutward expansion pressure exerted by the loose materials beingcompacted.

Once the convertible trailer 100 is unloaded at the unloading site, itmay be loaded again to backhaul bulk goods on the return trip, in orderto reduce transportation costs. If uncompressed bulk goods are to betransported, the convertible roof of the trailer 100 may be opened toallow the loading of the convertible trailer 100 from the top. Forinstance, the trailer 100 may be loaded with bulk goods like sand,gravel, or the like using a conventional loader 110. FIG. 2 is a rearview of the container of convertible trailer 100 when the panels 102 and104 are 90 degrees open, and the access door 202 is closed, while FIG. 3is a rear view of the container of the convertible trailer 100 when thepanels 102 and 104 are fully open (270 degrees), and the trailer isbeing loaded from the top.

As shown in FIGS. 1 to 3, panels 102 and 104 are movable between aclosed position, in which, the panels are substantially parallel andcoplanar so as to form a solid hard roof as shown in FIG. 1, and an openposition, in which, the panels are 270 degrees rotated from the closedposition and, in which, the panels are substantially parallel to theleft and right sidewalls of the trailer, as shown in FIG. 3.

When panels 102 and 104 are in the closed position, at least one lockingbar 106 secures both panels to each other. The locking bar 106 may beprovided on one of the panels or on both. FIG. 4 is an exploded viewshowing by way of example the locking bar 106 provided at both panels,in accordance with an embodiment of the invention. The locking bar 106may be welded or permanently secured to one of the panels at one sideand has one or more openings 400 at the other side, as illustrated inFIG. 4. The openings 400 provided in the locking bar overlap one or morethreaded openings 402 in the other panel when the panels are in closedposition for releasably securing the locking bar 106 to the other panelusing bolts or the like.

Panels 102 and 104 are connected to the sidewalls 112, 114 of thetrailer by hinges 108 as shown in FIGS. 1 and 4. The locking bar 106 isprovided adjacent, and preferably aligned with the hinges 108 forconnecting the sidewalls 112 and 114 to each other against the outwardexpansion pressure exerted by the loose materials being compacted andfor preventing the sidewalls and the roof from bulging out anddeforming.

Panels 102 and 104 are provided with a rotation mechanism that allowsthem to move between the closed position shown in FIG. 1, and the openposition shown in FIG. 3. FIG. 5 illustrates, by way of example, anembodiment of the rotation mechanism that rotates the panels. As shownin FIG. 5, the rotation mechanism includes a bracket 502 and a wormdrive or any other suitable rotating means 504. The bracket 502 isprovided at the side of each of panels 102 and 104, and connected to thepanel at one end and to the motor 504 at the other end.

In a preferred embodiment of the roof construction of the trailer 100,as shown in FIGS. 6 to 9, the roof 600 includes a pair of opposite rigidpanels 102, 104, respectively pivotally connected to opposite side wallsof the container by multiple hinges 108 for movement between a closedposition as shown, wherein each panel forms part of a solid roof forloading of the container with loosely compressed materials from theaccess door, and an open position (not illustrated) wherein thecontainer can be loaded from the top with bulk material. The containerincludes a plurality of spaced apart locking bars 106, distributed inlongitudinal direction of the roof 600, for securing the panels 102, 104in the closed position and for strengthening the sidewalls 112, 114 (seeFIGS. 2 and 9) against outward pressure exerted by the looselycompressed materials when loaded in the container, a spacing of thelocking bars 106 being smaller proximal to than distal from the accessdoor 202 (see FIG. 2).

Each locking bar 106 is preferably secured to one of the panels 102, 104at one end and includes a structure 700 for releasably fastening anopposite end to the remaining structure of the container in such a waythat the panels are reliably maintained in the closed position. Forexample, the opposite end of the locking bar can be releasably fastenedto the other of the panels 102, 104 when the panels 102, 104 are in theclosed position, for releasably locking the panels 102, 104 in theclosed position. The other end of the locking bar 106, however, may alsoextend around the top edge of the sidewall and come to rest against thesidewall for releasable attachment thereto, when the roof panels are inthe closed position.

For added stability, each locking bar 106 is preferably providedadjacent to and substantially aligned with a pair of hinges 108respectively connecting one of the panels 102, 104 to the associatedsidewall 112 or 114, for connecting the opposite sidewalls 112, 114 toeach other by way of the locking bars 106 and against the outwardpressure exerted by the loosely compressed materials compacted in thetrailer. The locking bars 106 may be releasably fastened at each end inorder to allow for the complete removal of the locking bars 106 foropening of the roof panels 102, 104 in restricted space situations, orto allow the roof panels 102, 104 to be opened with the locking bars 106attached to one or the other of the roof panels 102, 104.

In another aspect, the container as illustrated in FIG. 10, includes atie bar 120 connecting a top edge of the sidewalls 112, 114 mid span ofthe trailer for added structural strength of the basic trailerstructure, and a locking bar 106 located directly above the tie bar. Inanother aspect, the number of locking bars 106 between the tie bar 120and an access door end 204 of the container, the access door half of theroof, is higher than the number of locking bars 106 between the tie bar120 and the other end on the trailer. The number of locking bars 106 onthe access door half is preferably at least double the number on theother half. The tie bar 120 is located mid span of the trailer and isalways bolted at two locations to the structural top rail member 122(see also FIG. 11) that is located at the top of the trailer sidewalls112, 114 and which spans from sidewall 112 to sidewall 114.

As illustrated in FIGS. 11 and 13, each hinge 108 includes an outerhinge profile 108 a welded to an outer surface 105 of one of the roofpanels 102, 104 and a middle hinge profile 108 b welded to the top rail122 of one of the sidewalls 112, 114. A rubber seal 124 is inserted intoa seal slot 125 on the extruded roof panel 102 or 104. The rubber seal124 has a curved profile allowing it to curl on top of the top rail 122and rest on the top rail 122 when the roof panel 102, 104 is closed. Therubber seal 124 acts as a seal to prevent fill in the trailer escapingfrom the container and to prevent humidity entering the container.

As illustrated in FIG. 12, the roof panels 102, 104 respectively includeat their meeting edges a top overlap extrusion 126 and a bottom overlapextrusion 128. The top and bottom overlap extrusions 126, 128 overlapand interlock when the panels 102, 104 are in the closed position, asshown in FIG. 12. The top overlap extrusion 126 is provided with arubber seal extrusion 127 and a rubber seal 130, which runs the lengthof the bottom overlap extrusion 128 and engages the opposite roof panelto prevent material from exiting or entering the container in themeeting area of the roof panels 102, 104, when the panels are in theclosed position. A rubber seal cap 132 is provided on the lip 134 of thebottom overlap extrusion 128 to provide a seal between the top andbottom overlap extrusions 126, 128 and to prevent metal to metal contactat the meeting edge of the panels 102, 104.

FIG. 14 illustrates the end construction of the roof of the container ofthe invention and shows a rubber seal extrusion 136 mounted to a bottomsurface of the roof panel 102, 104 and a rubber seal 138 inserted intothe extrusion to seal the gap between the roof panel 102, 104 and thetop of the end wall, here represented by the angle bracket 142, which iswelded to the end wall (not shown). A bolt 140 can be used to secure theroof panel 102, 104 to the end wall by fastening it to the angle bracket142. Angle bracket 142 is welded to a structural rear header (not shown)located at the rear of the trailer. The rear header spans fromstructural post to structural post on the trailer body. This allows theplacement of two bolts at the very rear of the roof to anchor the roofto a structural member of the container body. DETACLAD material is anexplosion welded sandwich of aluminum and steel, in order to avoidelectrolytic corrosion between the steel and aluminum portions. DETACLADmaterial is welded to the angle bracket allowing a nut to be welded inplace, which allows the tie down bolt to fasten the roof in place. Thefront end construction is assembled accordingly with the angle bracketattached to a front header. Rubber seals are provided at the front endas well.

As illustrated in FIGS. 15 to 17, the tie down assembly 300 is an upsidedown assembly which allows a tie down bolt to be tightened from insidethe trailer, obviating the need for the operator to climb on top of thetrailer to lock down the roof. It would of course also be possible toinstall the tie down bolt in an upright orientation in which the tiedown bolt is fastened from on top of the roof.

The illustrated tie down assembly 300, includes the locking bar 106 andthe tie down bolt assembly 320. The locking bar 106 is an aluminumextrusion 302 with a generally C-shaped cross-sectional profile withhollow arms 304 and bottom grooves 306 incorporated into the arms of theextrusion for receiving and holding a rubber seal 308. The tie down boltassembly 320 includes the threaded tie down bolt 322, a handle 324welded to the bolt 322 for ease of rotation and tightening of the bolt322, and a nut 326 for threaded engagement by the bolt 322. An accessopening 328 is cut into the extrusion 302 at the location of the tiedown bolt assembly 320 to recess the assembly into the locking bar 106to allow for an optimum volume of the trailer (due to overall heightrestrictions). A top stiffener plate 330 is welded to the extrusion 302in the access opening 328 to stiffen up the locking bar 106 where thearm will be tightened down by the tie down bolt assembly 320. A bottomstiffener plate 332 is welded to the underside of the roof panel 102,104 to stiffen up the panel where the panel will be engaged by the tiedown bolt assembly 320. Both stiffener plates 330, 332 are preferablyprovided with a slot profile 334 for receiving the bolt 322, in order toallow for adjustment of the bolt location during bolt installation aswell as to absorb some shifting in the roof fore and aft during twistingand turning of the container. The nut 326 for engagement by the bolt 322is welded to the top stiffener plate 330. A washer 336 is welded to thebolt to prevent the bolt from falling through the roof during boltrelease from the nut 326.

At least one of the stiffener plates 330, 332 is preferably made ofDETACLAD material. If the top stiffener plate 330 is made of DETACLADmaterial (see FIG. 15), the edges 330 a of the DETACLAD material arepreferably beveled to allow for welding it inside the access opening 328to the inwardly projecting arms 303 of the extrusion 302. If the bottomstiffener plate 332 is made of DETACLAD material (see FIG. 16), the nut326 is welded to a flat steel washer 327, which rests on top of the topstiffener plate 330.

The rubber seal 308 is inserted into the bottom grooves 306 of thelocking arm extrusion 302 to allow for some cushioning between thelocking bar 106 and the roof panel 102, 104 to avoid metal resting onmetal.

A slot profile 340 is cut through the roof panel 102, 104 to accommodatethe tie down bolt 322. The slot profile 340 runs from the front to theback to allow for some movement in the locking bar 106 front to rear ofthe trailer.

At the location of the mid span tie bar 120, the tie down bolt 322extends not only through the roof panel 102, 104, but also through thetie bar 120 and the bottom stiffener plate 332 is welded to the bottomsurface of the tie bar 120 (see FIG. 17). Rubber seal profiles 344 restbetween the extruded aluminum roof panel 102, 104 and the mid span tiebar 120 localized around the region of the tie down assembly 300 forcushioning between the panel and the tie bar.

Although tie down arrangements in the form of a nut and bolt assemblyare disclosed in detail, other tie down arrangements which provide for areliable and releasable fastening of the free half of the locking bar tothe second roof panel can be used. For example, the tie down arrangementmay be provided by a pair of eyelets, one each on the free end of thelocking bar and on the second the roof panel (not illustrated), whichare positioned to be adjacent and co-centric when the roof is closed,and by a locking bar which is movable between a locked position in whichit fittingly extends through both eyelets and an unlocked position inwhich the locking bar is positioned clear of both eyelets. Other tiedown arrangements which reliably and releasably lock the roof panels inthe closed position can be used.

While the embodiments shown in FIGS. 1 to 17 illustrate a longitudinalcontainer, it is possible to implement the convertible roof of theinvention in a trailer having oval, cylindrical, or any polygonal shapedcontainer including a floor, a sidewall, and an access door for loadingcompressed materials when the convertible roof is in closed position.

Furthermore, different locks may be used for locking the panels inclosed positions for connecting opposite sidewalls by the locking baragainst the outward pressure of the compressed materials. Theimplementation and details of such locks are known in the art, and willnot be described in detail herein.

In the preceding description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe embodiments of the invention. However, it will be apparent to oneskilled in the art that these specific details are not required in orderto practice the invention.

The above-described embodiments of the invention are intended to beexamples only. Alterations, modifications and variations can be effectedto the particular embodiments by those of skill in the art withoutdeparting from the scope of the invention, which is defined solely bythe claims appended hereto.

1. A container for a convertible trailer including a chassis forcarrying the container and a set of wheels for rollably supporting thechassis on the ground, the container comprising a floor, a wall, a roof,and an access door for loading loosely compressed materials into thecontainer, the roof including a pair of opposite rigid panels,respectively pivotally connected to opposite side walls of the containerby multiple hinges for movement between a closed position wherein eachpanel forms part of a solid roof for loading of the container withloosely compressed materials from the access door, and an open positionwherein the container can be loaded from the top with bulk material, anda plurality of spaced apart locking bars distributed in longitudinaldirection of the roof, for selectively maintaining the panels in theclosed position against outward pressure exerted by the looselycompressed materials when loaded in the container and for strengtheningthe wall against the outward pressure, a spacing of the locking barsbeing smaller proximal to than distal from the access door, wherein eachlocking arm has an attached half, which is rigidly welded to a first ofthe pair of roof panels and a free half for resting against andreleasable attachment to the second of the pair of roof panels, when theroof panels are in the closed position; wherein the free half of thelocking bar is respectively releasably fastened to the second roof panelby a nut and bolt connection; and, wherein the nut is rigidly attachedto one of the roof panel and the locking bar and the bolt extendsthrough the other of the roof panel and the locking bar for engaging thenut and fastening the locking bar to the roof panel when the bolt istightened in the nut.
 2. The container of claim 1, wherein a firstrubber seal is provided between each roof panel and edges of thecontainer walls adjacent the panel in the closed position to minimizespillage of bulk materials carried in the trailer and intrusion ofmoisture and dirt into the container when the roof is closed.
 3. Thecontainer of claim 2, wherein a second rubber seal is provided betweenthe panels at their meeting edges.
 4. The container of claim 1, whereinthe roof panels are extruded panels and include edge extrusions foroverlapping and interlocking engagement of the roof panels at theirmeeting edges when in the closed position.
 5. The container of claim 4,wherein the edge extrusions are constructed as a bottom overlapextrusion extending along the meeting edge of one panel and a topoverlap extrusion extending along the meeting edge of the other paneland complementary to the bottom overlap extrusion.
 6. The container ofclaim 1, wherein the container is rectangular shaped, and the wall ofthe container includes a rear wall, a front wall and two oppositesidewalls and each locking bar is provided adjacent and substantiallyaligned with a pair of hinges respectively connecting one of the panelsto the associated sidewall, for connecting the opposite sidewalls toeach other by way of the locking bars and against the outward pressureexerted by the loosely compressed materials compacted in the trailer. 7.The container of claim 6, wherein the locking bars are releasablyfastened at each end in order to allow for the complete removal of thelocking bars for opening of the roof panels in restricted spacesituations, or for opening of the roof panels with the locking barsattached to one or the other of the roof panels.
 8. The container ofclaim 6, wherein the locking bars are positioned on the roof panels tobe in symmetrical contact with the roof panel on each side.
 9. Thecontainer of claim 8, wherein the container includes a tie barconnecting a top edge of the sidewalls mid span of the trailer for addedstructural strength of the basis trailer structure, and a locking barlocated directly above the tie bar.
 10. The container of claim 9,wherein the number of locking bars between the tie bar and an accessdoor end of the container, the access door half of the roof, is higherthan the number of locking bars between the tie bar and the other end onthe trailer.
 11. The container of claim 10, wherein the number oflocking bars on the access door half is at least double the number onthe other half.
 12. The container of claim 11, including at least 6locking bars on the access door half of the roof for added stability,resistance to movement and twisting and for resistance to compactingpressure exerted from the access opening.
 13. A convertible trailer,comprising a chassis, a set of wheels for rollably supporting thechassis on the ground, and a container according to any one of claims 1to 5 mounted on and supported by the chassis.
 14. A container for aconvertible trailer including a chassis for carrying the container and aset of wheels for rollably supporting the chassis on the ground, thecontainer comprising a floor, a wall, a roof, and an access door forloading loosely compressed materials into the container, the roofincluding a pair of opposite rigid panels, respectively pivotallyconnected to opposite side walls of the container by multiple hinges formovement between a closed position wherein each panel forms part of asolid roof for loading of the container with loosely compressedmaterials from the access door, and an open position wherein thecontainer can be loaded from the top with bulk material, and a pluralityof spaced apart locking bars distributed in longitudinal direction ofthe roof, for selectively maintaining the panels in the closed positionagainst outward pressure exerted by the loosely compressed materialswhen loaded in the container and for strengthening the wall against theoutward pressure, a spacing of the locking bars being smaller proximalto than distal from the access door; wherein each locking arm has anattached half, which is rigidly welded to a first of the pair of roofpanels and a free half for resting against and releasable attachment tothe second of the pair of roof panels, when the roof panels are in theclosed position; and, wherein a rubber seal is provided on the lockingbar for cushioning between the free half and the second panel to preventgrinding of the locking bar against the second panel.
 15. A convertibletrailer, comprising a chassis, a set of wheels for rollably supportingthe chassis on the ground, and a container according to claim 14 mountedon and supported by the chassis.
 16. A container for a convertibletrailer including a chassis for carrying the container and a set ofwheels for rollably supporting the chassis on the ground, the containercomprising a floor, a wall, a roof, and an access door for loadingloosely compressed materials into the container, the roof including apair of opposite rigid panels, respectively pivotally connected toopposite side walls of the container by multiple hinges for movementbetween a closed position wherein each panel forms part of a solid rooffor loading of the container with loosely compressed materials from theaccess door, and an open position wherein the container can be loadedfrom the top with bulk material, and a plurality of spaced apart lockingbars distributed in longitudinal direction of the roof, for selectivelymaintaining the panels in the closed position against outward pressureexerted by the loosely compressed materials when loaded in the containerand for strengthening the wall against the outward pressure, a spacingof the locking bars being smaller proximal to than distal from theaccess door; wherein each locking bar is preferably secured to one ofthe panels at one end and includes a structure for releasably fasteningan opposite end to another part of the container when the panels are inthe closed position, for releasably locking the panels in the closedposition; wherein the container is rectangular shaped, and the wall ofthe container includes a rear wall, a front wall and two oppositesidewalls and each locking bar is provided adjacent and substantiallyaligned with a pair of hinges respectively connecting one of the panelsto the associated sidewall, for connecting the opposite sidewalls toeach other by way of the locking bars and against the outward pressureexerted by the loosely compressed materials compacted in the trailer;wherein the locking bars are releasably fastened at each end in order toallow for the complete removal of the locking bars for opening of theroof panels in restricted space situations, or for opening of the roofpanels with the locking bars attached to one or the other of the roofpanels; and wherein a rubber seal profile is provided between the tiebar and the roof panels for cushioning.
 17. A convertible trailer,comprising a chassis, a set of wheels for rollably supporting thechassis on the ground, and a container according to claim 16 mounted onand supported by the chassis.
 18. A container for a convertible trailerincluding a chassis for carrying the container and a set of wheels forrollably supporting the chassis on the ground, the container comprisinga floor, a wall, an access door for loading loosely compressed materialsinto the container, a roof including a pair of opposite rigid panels,respectively pivotally connected to opposite side walls of the containerby multiple hinges for movement between a closed position wherein eachpanel forms part of a solid roof for loading of the container withloosely compressed materials from the access door, and an open positionwherein the container can be loaded from the top with bulk material, aplurality of spaced apart locking bars distributed in longitudinaldirection of the roof, for selectively maintaining the panels in theclosed position against outward pressure exerted by the looselycompressed materials when loaded in the container and for strengtheningthe wall against the outward pressure, a spacing of the locking barsbeing smaller proximal to than distal from the access door; each lockingbar having an attached half, which is attached to a first of the pair ofroof panels and a free half for resting against and releasableattachment to the second of the pair of roof panels, when the roofpanels are in the closed position; and a rubber seal provided on eachlocking bar for cushioning between the free half and the second panel toprevent grinding of the locking bar against the second panel.
 19. Thecontainer of claim 18, wherein the attached half is permanently attachedto the first of the pair of roof panels.
 20. The container of claim 18,wherein the container is rectangular shaped and the wall of thecontainer includes a rear wall, a front wall and two opposite sidewallsand the container further includes a tie bar connecting a top edge ofthe sidewalls mid span of the trailer for added structural strength ofthe container structure, a locking bar located directly above the tiebar and a rubber seal profile positioned between the tie bar and theroof panels for cushioning.
 21. The container of claim 20, wherein atthe location of the mid span tie bar, the tie down bolt extends not onlythrough the roof panel, but also through the tie bar.
 22. The containerof claim 21, wherein a bottom stiffener plate is welded to the bottomsurface of the tie bar to stiffen up the tie bar where the tie bar willbe engaged by the tie down bolt assembly.
 23. The container of claim 18,wherein the free half of each locking bar is respectively releasablyfastened to the second roof panel by a tie down bolt assembly.
 24. Thecontainer of claim 23, wherein tie down bolt assembly includes athreaded tie down bolt and a threaded nut for engagement by the bolt,the bolt including a handle welded to the bolt for ease of rotation andtightening of the bolt in the nut.
 25. The container of claim 24,wherein a washer is welded to the bolt to prevent the bolt from fallingthrough the roof during bolt release from the nut.
 26. The container ofclaim 24, wherein the threaded nut is rigidly attached to one of theroof panel and the locking bar and the tie down bolt extends through theother of the roof panel and the locking bar for engaging the nut andfastening the locking bar to the roof panel when the bolt is tightenedin the nut.
 27. The container of claim 26, wherein a slot profile isprovided in the roof panel for accommodating the tie down bolt.
 28. Thecontainer of claim 27, wherein the slot profile runs in longitudinaldirection of the container for allowing some movement in the locking barfront to rear of the container.
 29. The container of claim 18, whereineach locking bar is an aluminum extrusion with a generally C-shapedcross-sectional profile with hollow arms and bottom grooves incorporatedinto the arms of the extrusion for receiving and holding the rubberseal.
 30. The container of claim 29, wherein an access opening isprovided in the extrusion at the location of the tie down bolt assemblyto recess the assembly into the locking bar for maximizing a volume ofthe container.
 31. The container of claim 30, further comprising a topstiffener plate welded to the extrusion in the access opening to stiffenup the locking bar where the bar will be tightened down by the tie downbolt assembly.
 32. The container of claim 31, further comprising abottom stiffener plate welded to an underside of the roof panel tostiffen up the roof panel where the roof panel will be engaged by thetie down bolt assembly.
 33. The container of claim 32, wherein bothstiffener plates are provided with a slot profile for receiving the tiedown bolt, in order to allow for adjustment of the bolt location duringbolt installation as well as to absorb some shifting in the roof foreand aft during twisting and turning of the container.
 34. The containerof claim 32, wherein at least one of the stiffener plates is made ofDETACLAD material, which is an explosion welded sandwich of aluminum andsteel portions, in order to avoid electrolytic corrosion between thesteel and aluminum portions.
 35. The container of claim 34, wherein thetop stiffener plate is made of the DETACLAD material and the edges ofthe stiffener plate are beveled to allow for welding it inside theaccess opening to inwardly projecting arms of the extrusion.
 36. Thecontainer of claim 34, wherein the bottom stiffener plate is made of theDETACLAD material and the nut is welded to a flat steel washer whichrests on top of the top stiffener plate.